Fuels based on bio-component sources will likely become increasingly prevalent in the future. Already, various governments have instituted current and future requirements that motor fuel pools contain a minimum percentage of fuel derived from a bio-component source, such as a plant, animal, fish, or algae based oil or fat.
One current technique for creating diesel range fuels from a bio-component feed is to convert triglycerides into fatty acid alkyl esters, such as fatty acid methyl esters (FAME), by transesterification. Typical products of a transesterification reaction are glycerol and fatty acid alkyl esters that roughly correspond to the fatty acid chains of the original triglycerides and to the alkyl alcohol(s) used for transesterification. The transesterification reaction can be catalyzed using an acid, but typically base catalyzed reactions are used due to faster reaction rates.
The fatty acid methyl esters typically produced for use in diesel fuel have a number of drawbacks. For example, fatty acid methyl esters having saturated carbon chains of about C14 to about C20 in length and that boil in the diesel range typically have poor cold flow properties. On the other hand, unsaturated fatty acid methyl esters having carbon chains of about C14 to about C20 in length typically have acceptable cold flow properties but are more susceptible to oxidation. Thus, more suitable compounds for use as biodiesel would be desirable.
U.S. Pat. No. 5,840,942 describes a method for adding aryl hydrocarbons across an olefin in a fatty acid or fatty ester. The addition of the aromatic group is catalyzed using a clay or zeolite with acidic properties. The reaction is carried out at pressures of 50 psig to 200 psig (350 kPag to 1.4 MPag).
U.S. Pat. No. 5,034,161 describes a method for adding aryl hydrocarbons across an olefin in an aliphatic hydrocarbon. The addition of the aromatic group is catalyzed using a superacid.
Japanese Published Patent Application No. 06-313188 describes a method for producing fatty acid esters from triglycerides. The triglyceride is exposed to an alcohol in the presence of a solid acid catalyst. Reaction pressures at or near atmospheric pressure are described.
U.S. Pat. No. 7,488,837 describes methods for forming a fatty acid alkyl ester. One of the methods involves exposing a vegetable oil to alcohol in the presence of a resin foamed article that incorporates acidic functionality. Sulfonic acid groups are mentioned as a possible acid functionality for the resin foam. Temperatures from 50° C. to 120° C. and reaction pressures near atmospheric pressure are described.
U.S. Pat. No. 5,426,199 describes a method for preferentially forming esters rather than ethers during reaction of organic acids or esters with alcohols. The method includes exposing the organic acid or ester to the alcohol in the presence of vinylaromatic polymer beads that have been modified on the surface to include acidic functionality. Sulfuric acid and chlorosulfonic acid are mentioned as functionalizing agents for the beads. The interior of the beads is not functionalized. With regard to reaction conditions, temperatures below 130° C. are described due to the stability of the beads, and pressures near atmospheric are described.
U.S. Pat. No. 5,003,124 describes a method for reacting C4 or C5 olefins with C1 to C6 alcohols in the presence of an acid functionalized vinylaromatic bead catalyst. The process is described as causing oligomerization and etherification. The process is conducted at the boiling point of the reaction mixture.
U.S. Published Patent Application No. 2007/0142690 describes a process for making a distillate fuel or lubricant composition. The process includes reacting a C5 or larger olefin with an isoparaffin in the presence of an ionic liquid catalyst.